In video presentation additional information is often presented with the video as an overlay. Such overlays are used in television, scientific observation, surveillance and many other fields. Common overlays provide sports scores and statistics, news tickers, legends to identify a player, a speaker, an object on the screen, or some other background or contextual information for the video. Typically the overlays are added during a production or a post-production stage and are a part of the video. They cannot be removed, changed or added to by the viewer.
Visual tags identifying the presence and location of still or moving objects are built in to many video editing tools. Some video editing tools even have a motion tracking feature that allows a tagging graphic to be added to the video that follows the position of a moving object. Motion tracking software can be used to follow an object in the video after an editor tags that object. The tagging graphic is then composited onto the video content and will be seen whenever the composite video is played.
Selectable overlays have been developed as overlays that a viewer can select to turn on and off. This may have benefits for those viewers that wish to see more of the video without the selectable overlay blocking a portion of the screen. To allow an overlay to be turned off, the overlay is presented separate from the video data. Overlays may be sent over separate transmission channels or separately as embedded metadata. Additional rendering capabilities are used at the receiver, such as a set-top box or display, to render a pixel representation from the metadata. The production workflows are modified for selectable overlays to render the overlays in a separate format, such as meta-data.